Measures differ for gold, gemstones

While the world of metal and gem values can be confusing, one of the first things you need to know to understand things is the difference between "karats" and "carats."

The words sound identical but are spelled differently and have vastly different meanings. Both act as simple indicators to listen for to help you quickly assess a general range of value.

Karats or karatage always refers to gold. (Other noble metals, such as platinum and silver, have their own standards of purity.)

Karat indicates the purity or fineness of gold, according to the Gemological Institute of America. The purity of gold is assessed in measures of parts per 1,000. The purer the gold, the higher the karat number. The lower the number, the higher the alloy content and the lower the gold content.

The term is often abbreviated as "K" or "KT". It is generally preceded by a number indicating the ratio of gold content relative to the parts of other metal that it is mixed with.

Gold pieces carry a stamp that indicates their purity. There are different types of stamps that are regulated in America by the Federal Trade Commission. These industry standards were developed in 1957, and remain in force today.

These guidelines dictate that it is a violation to use the word gold to describe an item that is not entirely made of gold, according to the GIA. It may only be used to describe 24KT gold, which is 99.99 percent pure. This is where the karatage numbers come into play. The information below is based on material that the GIA uses to train its gemological students on karats and their equivalents.

Some of the most common ratings tell you exactly what you are getting when you buy gold.

10K is 41.7 percent pure gold, or 417 parts per 1,000 gold. It is also 10 parts gold and 14 parts other metal.

14K is 58.3 percent pure gold, or 583 parts per 1,000 gold. It is also 14 parts gold and 10 parts other metal.

18K is 75 percent pure gold, or 750 parts per 1,000 gold. It is also 18 parts gold and 6 parts other metal.

24K is 99.99 percent pure gold, or 999 parts per 1,000 gold. It is also 24 parts gold and 0 parts other metal.

When you hear about the price of gold on the open market, it is talking about the value of 24KT gold. Therefore, it is fair to assume that the purer the gold content of an item, the greater the value.

When two metals are mixed together, it creates an alloy. Mixing other metal with gold is designed to enhance certain desirable features in gold, while making it more affordable. According to the GIA, some of the reasons for doing this include increased workability and durability, and to improve or alter the appearance.

Choosing specific metals is a matter of taste and how you intend to use your metal. If you seek something that is durable and perfect for everyday hard knocks, you may choose 10KT or 12KT pieces for rings. However, if you prefer the deep rich allure of golden hue, you may opt for 18KT gold.

Meanwhile, 24KT gold pieces are soft and luxurious, but they are also rarer, which causes them to be more expensive.

If you prefer the bright appeal of white gold, know that it is really just an alloyed version of 24KT gold.

Carats

Carat refers to the method by which diamonds and colored gemstones are measured by weight, not purity. It also does not really indicate true size. Since 1913, most countries agree that a carat weighs 200 milligrams, or one-fifth of a gram, according to the book "Jewelry and Gems, the Buying Guide," by Antoinette Matlins.

If someone is describing the carat weight of a gemstone, such as her new 5 ct. amethyst, then the numbers will not fall the specific ratios gold would.

An easy indicator is to listen carefully to what someone is describing. If they are describing a stone, then they are offering carat weight. If they are describing white or yellow gold, then they are offering karat information.